


Applied Ecology

by kylermalloy



Category: Fullmetal Alchemist - All Media Types
Genre: Alternate Universe - Vampire, Biology Terms, Blood Drinking, Elricest, Gen, Implied/Referenced Incest, Introspection, M/M, Vampire Alphonse Elric, because Al’s a nerd and so am I, here have a community-style title, is this inaccurate to real biology? heck yes but I do what I want, it works when I’m stuck thinking of something witty and profound for a title
Language: English
Status: Completed
Published: 2021-02-12
Updated: 2021-02-12
Packaged: 2021-03-12 04:54:48
Rating: Teen And Up Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 947
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/29379540
Author URL: https://archiveofourown.org/users/kylermalloy/pseuds/kylermalloy
Summary: Symbiosis, n.Any of several living arrangements between two different organisms living in close physical association, typically to the advantage of both.Al reflects on the nature of his and Ed’s relationship, according to science.
Relationships: Alphonse Elric/Edward Elric
Comments: 7
Kudos: 10
Collections: Vampire!Al AU





	Applied Ecology

**Author's Note:**

> This fic is set in the vampire!Al AU—summarized in [this tumblr post](https://kylermalloy.tumblr.com/post/642494081155612672/the-amount-of-narrative-shuffling-it-would-take).

The word sat undisturbed in one of Dad’s many books for years. Ed and Al skimmed through the chapters on ecosystems and adaptation—more interested in the makeup of the human body.

**_Symbiosis, n._ ** _ Any of several living arrangements between two different organisms living in close physical association, typically to the advantage of both. _

.

On Yock Island they witnessed it firsthand; only after two weeks of near starvation, some attempted brother-on-brother cannibalism, and completely unprompted bug-eating did the answer come to them.

Al’s hunger-ridden brain took hours to dredge up the scientific explanation for  _ all is one. _ “Brother, didn’t we read about that? Everything in nature helps each other out—that’s symbiosis.”

“Yeah, sort of. But it’s sym- _ bee _ -osis.”

“No, it’s sym- _ bi _ -osis. Like  _ bi _ -ology.”

“Sym- _ bee _ -osis. I’m older; I know better.”

“Whatever.”

.

It was ironic, Al reflected, for all their musings and studies on equivalent exchange in alchemy, that they’d hardly noticed it happening all around them. In nature, and among their fellow humans.

.

**_Mutualism, n._ ** _ An interaction between two or more organisms that results in positive (beneficial) effects on per capita reproduction and/or survival of the interacting populations. _

When Ed joined the military, many likened it to selling his soul. Granny Pinako shook her head, mumbling that he’d regret it after years of having a leash around his neck.

(And Ed did grumble a fair bit, Al had to admit.)

Yet there was a mutual benefit. While Ed sacrificed his alchemic talents and much of his time to the State, he received a great deal of money, clout, and access to restricted knowledge.

However much he complained about  _ Mustang this, military dog that, _ there was a reason he’d done it. The same reason Colonel Mustang put up with the teenage nuisance that was the Fullmetal Alchemist—the ends justified the means. In spite of Ed’s abundant and sprawling attitude, the military had a talented alchemist in their pocket. And in return, Ed got the funding and resources he’d need to find a way to save Al.

(They’d succeed someday, right?)

(Right.)

.

**_Commensalism, n._ ** _ A relationship between two individuals in which one organism obtains food or other benefits from the other without either harming or benefitting the latter. _

If anyone had asked Trisha Elric how she benefitted from raising two boys, she would have talked at length about the joy they brought her, the love she had for them, and how much better her life was with her sons in it.

But looking at it from the perspective of a scientist, Al knew the benefits were mostly…decorative.

He and Ed existed off the life their mother built for herself in Resembool, giving her little or nothing in return.

Such was the life of a parent, he supposed. Providing for children who could provide next to nothing in return.

(She might have reaped the benefits—if she had survived into old age, and her children had the opportunity to care for her. Life, though, wasn’t so generous.)

It wasn’t too unlike what Izumi had done for them, either—taking them in and teaching them alchemy, knowing they could do little for her in return.

In nature, Al knew, the second party was often unaware of the benefit it provided to the first. An unknowing partnership.

It was different with humans, though. Intentional provision with no benefit to the self had to come from a truly altruistic being.

.

There was a fair amount of altruism in the third form as well, Al realized. In his case, at least.

(This one just hurt a lot more.)

.

**_Parasitism, n._ ** _ A long-term relationship between two organisms, wherein one member, the parasite, gains benefits that come at the expense of the host. _

It was glaringly obvious, when you thought about it. 

_ Teeth bared, biting, almost chewing through layers of skin. _

Even someone with no scientific background could parse this. In fact, Al was pretty sure he’d had the word thrown at him before, somewhere.

( _ Parasite. _ Sure sounded like something Envy would say.)

_ Lips locking around the fresh wound, like a deadly kiss. _

Alphonse Elric could not survive on his own. Without the blood of his brother, he would fade from hunger to fatigue to a deathlike coma. He  _ needed _ Ed to provide for him—otherwise he wouldn’t survive.

_ Tongue sweeping, lapping at the hot blood that flowed freely. Sucking life and giving nothing back. _

When anyone asked young Al what he wanted to be when he grew up, he’d never considered answering  _ parasite. _

Yet here he was—a creature who survived at the expense of another. At the expense of his own brother.

A leech. A bloodsucking freak.

And Ed?

_ Hands holding him down, holding him in place as his body flinched and fought against the painful invasion. _

Ed didn’t really have a choice. (The choice was either  _ bleed _ or  _ let Al die. _ )

_ Hands, soft despite the pain, lacing in his unkempt hair. Whispering reassurance and encouragement through gritted teeth. Drink; it’s okay…take all you need. _

And he always chose to bleed.

_ Lips, a little warmer now and much redder, caressing the broken skin. _

A thanks and a promise— _ I’ll be back. _

.

Parasites in nature weren’t cursed with a conscience, with guilt.

Al was just that lucky.

.

“I’d do it again.” Ed’s voice is rough, scraping against the groans of pain lodged in his throat.

Al’s face is buried in his hands. He doesn’t see Ed scooting closer before an arm is wrapped around his shoulders. Lips whisper in his ear. “I’d do it a thousand times over.”

.

Host organisms in nature didn’t sacrifice out of altruism, out of love.

(Al was just that lucky.)

**Author's Note:**

> Thanks for reading! Let me know what you think—comments feed my SOUL. Check out the [vampire!Al collection](https://archiveofourown.org/collections/Vampire_Al_AU) for more fics, and come say hi to me on [tumblr](https://kylermalloy.tumblr.com)!


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